The present invention relates generally to cooking devices, and more particularly provides structurally and operationally improved deep fat frying apparatus which, compared to conventional frying apparatus, is appreciably lighter in weight, less expensive to build and operate, has faster oil heating response times and better oil temperature control capabilities, and is provided with a frypot section having a unique construction which enables it to be more rapidly and thoroughly cleaned. Additionally, the frypot section has incorporated therein a shortening melter which significantly improves the initial solid shortening melting process used to form the cooking oil within the frypot.
Conventional deep fat fryers used in commercial cooking operations are typically provided with a metal frypot section in which a quantity of heated cooking oil is disposed. A variety of food items may be deep fried in the heated cooking oil by lowering them into the oil by means of wire frying baskets. A conventional method of heating the cooking oil is to provide a gas-fired burner structure which generates hot combustion gas that is flowed through various externally insulated, all-metal heating passages extending around the exterior of certain wall sections of the frypot. A suitable supply system is utilized to flow a gas-air mixture to the burner structure for combustion therein to generate the hot combustion gas.
A variety of problems, limitations and disadvantages are commonly associated with deep fat fryers of this general type. For example, the frypot section is typically fabricated from a variety of metal panels which are welded together at edge portions thereof to define the metal shell of the frypot. This conventional fabrication technique results in the frypot shell having angled interior corners along which weld joint lines extend. These angled interior corners render the periodic cleaning of the frypot interior somewhat difficult at such corner sections. Additionally, if the interior cleaning process is not carried out rather carefully, residual cooking oil can remain in the corners giving rise to a potential sanitation problem when a subsequent batch of cooking oil is placed in the frypot.
Another problem arises during the shortening melting process in which a large block of solid shortening is placed within the frypot to be melted to form the actual cooking oil. The conventional frypot has an upper section in which the actual food cooking is performed, and one or more smaller cross-sectioned well sections depending from the upper cooking section. Under conventional practice, the solid shortening block is placed in the upper frypot section so that it rests upon the bottom wall of such upper section and is disposed above the empty well portion of the frypot. To melt the shortening block it has heretofore been necessary to utilize the main heating system for the frypot, which normally supplies heat to the exterior walls of the frypot well sections. This main heating system typically has a capacity far in excess of that required to simply melt the solid shortening block. Accordingly, to prevent burning and/or smoking of the melted shortening which initially flows downwardly into the well section of the frypot, it has previously been necessary to "pulse" the main heating system to prevent overheating of the well section walls. This rather cumbersome shortening melting procedure requires a considerable amount of supervision and is basically a labor-intensive "hands on" process.
Alternatively, various auxiliary heating devices have been proposed to perform the initial solid shortening melting process. One such device is basically an electrically heated plate structure which has a series of openings formed therethrough and is rested on the bottom wall of the upper frypot section. With this heating plate in place, the shortening block is positioned on its upper surface and the plate's heating coils are energized. As the shortening is melted, it runs through the plate openings down into the unheated frypot well section. When all of the solid shortening is melted, the heating plate is lifted out of the frypot and the main oil heating process is initiated. While this alternate technique is somewhat less hazardous, it also requires worker supervision and is somewhat cumbersome and time consuming. Like the previously described main heating system pulsing process, the use of heated, drop-in plates is also a "hands on" process.
As previously mentioned, the hot combustion gas generated by the gas-fired burner structure is flowed through oil heating passages which are formed around suitable exterior surfaces of the frypot well section or sections. The conventional method of forming these passages is to form them from an auxiliary metal structure which abuts exterior wall surfaces of the metal frypot. The outer surface of this metal heating passage structure is typically exteriorly insulated with suitable insulation material. As the hot combustion gas from the gas-fired burner structure is flowed through these all-metal heating passages, a significant portion of the available combustion gas heat is unavoidably diverted into the significant mass of metal used to form the heating passages in conjunction with the frypot walls which are actually heated.
Stated in another manner, during the initial oil heating process, only a portion of the available combustion gas heat is transferred inwardly through the frypot shell wall into the heating oil-the balance of such heat is transferred outwardly into the other metal walls of the heating flow passages. Because of this relatively large metal mass into which the heat of the combustion gas can flow, the response time between the initiation of the oil heating process and the attainment of the desired operating temperature of the cooking oil has been correspondingly delayed. Additionally, the control of the temperature of the cooking oil is less precise than it might otherwise be.
Yet another problem is related to the supply systems used to provide to the gas-fired burner structure a gas-air mixture for combustion therein. Typically such supply systems include a forced air blower which flows a supply of pressurized air into the burners, and a gas supply system which forces a stream of gaseous fuel through a gas pressure regulator into the flowing air stream for mixture therewith and supply with the air stream to the burner structure. One problem associated with this conventional gas-air mixture supply system is the possibility that, upon regulator failure, gas can be flowed through the system in the absence of air flow. Another heretofore unavoidable problem associated with such supply systems is that when a blower outlet pressure drop is experienced (when, for example, a leak develops in the gas supply ductwork) the air-fuel mixture supplied to the frypot burners becomes richer, thereby resulting in fuel wastage.
It can readily be seen from the foregoing that a variety of improvements are needed in conventional deep fat fryers. Accordingly, it is an object of the present invention to provide a deep fat fryer which incorporates such improvements.